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FluidSynth(1) General Commands Manual FluidSynth(1)


FluidSynth - a SoundFont synthesizer


fluidsynth [options] [ SoundFonts ] [ midifiles ]


FluidSynth is a real-time MIDI synthesizer based on the SoundFont(R) 2 specifications. It can be used to render MIDI input or MIDI files to audio. The MIDI events are read from a MIDI device. The sound is rendered in real-time to the sound output device.

The easiest way to start the synthesizer is to give it a SoundFont on the command line: 'fluidsynth soundfont.sf2'. fluidsynth will load the SoundFont and read MIDI events from the default MIDI device using the default MIDI driver. Once FluidSynth is running, it reads commands from the stdin. There are commands to send MIDI events manually, to load or unload SoundFonts, and so forth. All the available commands are discussed below.

FluidSynth can also be used to play a list of MIDI files. Simply run FluidSynth with the SoundFont and the list of MIDI files to play. In this case you might not want to open the MIDI device to read external events. Use the -n option to deactivate MIDI input. If you also want to deactivate the use of the shell, start FluidSynth with the -i option: 'fluidsynth -ni soundfont.sf2 midifile1.mid midifile2.mid'.

Run fluidsynth with the --help option to check for changes in the list of options.


fluidsynth accepts the following options:

The audio driver to use. "-a help" to list valid options
Number of audio buffers
Turn the chorus on or off [0|1|yes|no, default = on]
Dump incoming and outgoing MIDI events to stdout
Audio file endian for fast rendering or aufile driver ("-E help" for list)
Load command configuration file (shell commands)
Render MIDI file to raw audio data and store in [file]
Set the master gain [0 < gain < 10, default = 0.2]
Defines the number of LADSPA audio nodes
Print out this help summary
Don't read commands from the shell [default = yes]
Attempt to connect the jack outputs to the physical ports
The number of midi channels [default = 16]
Don't connect to LASH server
The number of stereo audio channels [default = 1]
The name of the midi driver to use. "-m help" to list valid options.
Don't create a midi driver to read MIDI input events [default = yes]
Define a setting, -o name=value ("-o help" to dump current values)
Audio file format for fast rendering or aufile driver ("-O help" for list)
Set MIDI port name (alsa_seq, coremidi drivers)
Do not print welcome message or other informational output
Set the sample rate
Turn the reverb on or off [0|1|yes|no, default = on]
Start FluidSynth as a server process
Audio file type for fast rendering or aufile driver ("T help" for list)
Print out verbose messages about midi events (synth.verbose=1) as well as other debug messages
Show version of program
Size of each audio buffer


The settings to be specified with -o are documented in the fluidsettings.xml hopefully shipped with this distribution or online at . We recommend viewing this file in a webbrowser, favourably Firefox.


Prints out list of help topics (type "help <topic>" to view details on available commands)
Quit the synthesizer
Load a SoundFont
Unload a SoundFont. The number is the index of the SoundFont on the stack.
Lists the current SoundFonts on the stack
Print out the available instruments for the SoundFont.
Send a note-on event
Send a note-off event
Send a control change event
Send program-change message
Combination of bank-select and program-change
Print out the presets of all channels.
Set the master gain (0 < gain < 5)
Choose interpolation method for all channels
Choose interpolation method for one channel
Turn the reverb on or off
Change reverb room size
Change reverb damping
Change reverb width
Change reverb level
Turn the chorus on or off
Use n delay lines (default 3)
Set output level of each chorus line to num
Set mod speed of chorus to num (Hz)
Set chorus modulation depth to num (ms)
Reloads the default MIDI routing rules (input channels are mapped 1:1 to the synth)
Deletes all MIDI routing rules.
Starts a new routing rule for events of the given type
Limits the rule for events on min <= chan <= max. If the channel falls into the window, it is multiplied by 'mul', then 'add' is added.
Limits parameter 1 (for example note number in a note events). Similar to router_chan.
Limits parameter 2 (for example velocity in a note event). Similar to router_chan
Finishes the current rule and adds it to the router.
channels. Regardless of the channel, the synthesizer plays the note on ch 15 (synthchannel=midichannel*0+15)
Configures the modulation wheel to act as sustain pedal (transforms CC 1 to CC 64 on the lower 8 MIDI channels, routes to ch 15)


Peter Hanappe <>
Markus Nentwig <>
Antoine Schmitt <>
Josh Green <>
Stephane Letz <>
Tom Moebert <tom[d0t]mbrt[ÄT]gmail[d0t]com>

Please check the AUTHORS and THANKS files for all credits


SoundFont(R) is a registered trademark of E-mu Systems, Inc.

January 1, 2022